Color image forming apparatus and color image forming method

Abstract

A color image forming apparatus includes a color-shift-detection-image forming unit, a color shift detector, a recording-material color-shift correcting unit and a conveyance-unit color-shift correcting unit. The color-shift-detection-image forming unit selectively forms a color-shift detection image on a recording medium or a first conveyance unit. The color shift detector detects color shift based on the color-shift detection image. The recording-material color-shift correcting unit performs color-shift correction based on the color-shift detection information corresponding to the color shift on the recording medium. The conveyance-unit color-shift correcting unit performs color-shift correction based on an amount of change in the color-shift detection information corresponding to the color shift on the first conveyance unit. The amount of change is determined using the color-shift detection information corresponding to the color shift on the first conveyance unit, which is obtained after the recording-medium color-shift correcting unit performs the color-shift correction, as a reference.

1. A color image forming apparatus comprising:
 a plurality of image forming units that form a plurality of color-component images; 
 a recording material conveyance unit that conveys a recording material to locations corresponding to the respective image forming units; 
 a color-shift-detection-image forming unit that selectively forms a color-shift detection image on the recording material or the recording material conveyance unit at the respective image forming units; 
 a color-shift detector for detecting a color shift based on the color-shift detection image, which is selectively formed on the recording material or the recording material conveyance unit by the color-shift-detection-image forming unit; 
 a recording-material color-shift correcting unit that corrects a color-shift based on color-shift detection information on the recording material detected by the color shift detector; and 
 a conveyance-unit color-shift correcting unit that performs based on the color-shift detection information on the recording material conveyance unit detected by the color-shift detector after the color-shift correction by the recording-material color-shift correction unit as a reference, color-shift correction based on an amount of change of subsequent color-shift detection information on the recording material conveyance unit, which is obtained by the color-shift detector from the reference. 
 
   
   
     2. The color image forming apparatus according to  claim 1 , wherein the recording-material color-shift correcting unit performs the color-shift correction based on the color-shift detection information detected according to positions on the recording material. 
   
   
     3. The color image forming apparatus according to  claim 1 , wherein:
 the recording-material color-shift correcting unit detects a fixed image which has passed through a fixing device disposed on a downstream side of the recording material conveyance unit in a recording-material conveyance direction, and performs the color-shift correction based on the color-shift detection information. 
 
   
   
     4. The color image forming apparatus according to  claim 1 , wherein the conveyance-unit color-shift correcting unit performs the color-shift correction in accordance with a condition under which a use environment is changed. 
   
   
     5. The color image forming apparatus according to  claim 1 , wherein each of the recording-material color-shift correcting unit and the conveyance-unit color-shift correcting unit performs the color-shift correction in accordance with a condition under which a use environment is changed. 
   
   
     6. The color image forming apparatus according to  claim 1 , wherein:
 the recording-material color-shift correcting unit performs the color-shift correction at an initial stage, and 
 the conveyance-unit color-shift correcting unit performs second and subsequent color-shift corrections using a result of the color-shift correction performed by the recording-material color-shift correcting unit. 
 
   
   
     7. A color image forming apparatus comprising:
 a plurality of image forming units that form a plurality of color-component images; 
 a recording material conveyance unit that conveys a recording material to locations corresponding to the respective image forming units; 
 a color-shift-detection-image forming unit that selectively forms a color-shift detection image on the recording material or the recording material conveyance unit at the respective image forming units; 
 a color-shift detector for detecting a color-shift based on the color-shift detection image, which is selectively formed on the recording material or the recording material conveyance unit by the color-shift-detection-image forming unit; 
 a recording-material color-shift correcting unit that corrects image-formation start timings of the respective image forming units based on the color-shift detection information on the recording material detected by the color-shift detector, to perform a color-shift correction, and 
 a conveyance-unit color-shift correcting unit that corrects, based on the color-shift detection information on the recording material conveyance unit detected by the color-shift detector after the color-shift correction by the recording-material color-shift correction unit as a reference, the image-formation start timings of the respective image forming units based on an amount of change in subsequent color-shift detection information on the recording material conveyance unit detected by the color-shift detector from the reference, to perform the color-shift correction. 
 
   
   
     8. A color image forming apparatus comprising:
 a plurality of image forming units that forms a plurality of color-component images; 
 a recording material conveyance unit that conveys a recording material to locations corresponding to the respective image forming units; 
 a color-shift-detection-image forming unit that selectively forms a color-shift detection image on the recording material or the recording material conveyance unit at the respective image forming units; 
 a color-shift detector for detecting a color shift-based on the color-shift detection image formed selectively on the recording material or the recording material conveyance unit by the color-shift-detection-image forming unit; 
 a recording-material color-shift correcting unit that corrects output timings of latent images to be formed in the respective image forming units based on the color-shift detection information on the recording material detected by the color-shift detector, to perform a color-shift correction, and 
 a conveyance-unit color-shift correcting unit that corrects, based on the color-shift detection information on the recording material conveyance unit detected by the color-shift detector after the color-shift correction by the recording-material color-shift correcting unit as a reference, the output timings of the latent images to be formed in the respective image forming units based on an amount of change in subsequent color-shift detection information on the recording material conveyance unit detected by the color-shift detector from the reference, to perform the color-shift correction. 
 
   
   
     9. A color image forming apparatus comprising:
 a plurality of image forming units that forms a plurality of color-component images; 
 a recording material conveyance unit for conveys a recording material to locations corresponding to the respective image forming units; 
 a color-shift-detection-image forming unit that selectively forms a color-shift detection image on the recording material or the recording material conveyance unit at the respective image forming units; 
 a color-shift detector for detecting a color-shift based on the color-shift detection image formed selectively on the recording material or the recording material conveyance unit by the color-shift-detection-image forming unit; 
 a recording-material color-shift correcting unit that corrects a conveyance speed of the recording material based on the color-shift detection information on the recording material detected by the color-shift detector, to perform a color-shift correction, and 
 a conveyance-unit color-shift correcting unit that corrects, based on the color-shift detection information on the recording material conveyance unit detected by the color-shift detector after the color-shift correction by the recording-material color-shift correcting unit as a reference, image-formation start timings of the respective image forming units or output timings of latent images to be formed in the respective image forming units based on an amount of change of subsequent color-shift detection information on the recording material conveyance unit detected by the color-shift detector, to perform the color-shift correction. 
 
   
   
     10. The color image forming apparatus according to  claim 9 , wherein:
 the recording-material color-shift correcting unit corrects the conveyance speed of the recording material by a conveyance member disposed on an upstream side of the recording material conveyance unit in a recording material conveyance direction. 
 
   
   
     11. The color image forming apparatus according to  claim 9 , wherein:
 the recording-material color-shift correcting unit corrects the conveyance speed of the recording material by a fixing device disposed on a downstream side of the recording material conveyance unit in a recording-material conveyance direction. 
 
   
   
     12. A color image forming apparatus comprising:
 a plurality of image forming units that form a plurality of color-component images; 
 a recording material conveyance unit for conveying a recording material to locations corresponding to the respective image forming units; 
 a color-shift-detection-image forming unit that selectively forms a color-shift detection image on the recording material or the recording material conveyance unit at the respective image forming units; 
 a color-shift detector for detecting a color-shift based on the color-shift detection image formed selectively on the recording material or the recording material conveyance unit by the color-shift-detection-image forming unit; 
 a recording-material color-shift correcting unit that corrects a mechanical adjustment amount of a recording material conveyance member based on the color-shift detection information on the recording material detected by the color-shift detector, to perform the color-shift correction, and 
 a conveyance-unit color-shift correcting unit that corrects, based on the color-shift detection information on the recording material conveyance unit detected by the color-shift detector after the color-shift correction by the recording-material color-shift correcting unit as a reference, the mechanical adjustment amount of the recording material conveyance member based on an amount of change of the subsequent color-shift detection information on the recording material conveyance unit detected by the color-shift detector from the reference, to perform the color-shift correction.